1. Field of the Invention
The present invention relates to a method for manufacturing magnetic head suspensions used in magnetic disk devices and to a method for inspecting metal substrates used for the magnetic head suspensions.
2. Description of the Background Art
A plate-like support called magnetic head suspension is used in a magnetic disk device to position the magnetic head to a desired track on a rotating magnetic disk. The magnetic head suspension has a plurality of wiring patterns formed thereon, and it also has a magnetic head supporting portion (which is hereinafter referred to as tongue) formed near an end. In manufacture of the magnetic head suspension, an insulating layer, wiring patterns, and cover layer are formed in order on a metal substrate.
Recently, a method for mass production of the magnetic head suspensions is suggested, where the processes for formation of the insulating layer, wiring patterns, and cover layer are sequentially applied to a long-sized substrate in roll form which is continuously or intermittently transported (Japanese Patent Laying-Open No.10-320736).
FIG. 12 is a plane view showing the long-sized substrate used in the aforementioned conventional manufacturing method. As shown in FIG. 12, a plurality of rectangular regions 110, each defining a unit in exposure process, are formed in two lines along the length direction of the long-sized substrate 100. Each region 110 contains a plurality of magnetic head suspensions 101 formed in 6 columns and 16 rows.
Given processes are sequentially applied to each region 110 on the long-sized substrate 100 continuously or intermittently transported, whereby a number of magnetic head suspensions are formed at once on the long-sized substrate 100.
In order to attach a magnetic head on the tongue of the magnetic head suspension, the tongue is bent so that it forms a given angle with respect to the body of the suspension (the part of the magnetic head suspension except the tongue). In this process, the tongues of a plurality of magnetic head suspensions must be bent at a constant angle.
However, the long-sized substrate wound in a roll has a certain amount of warp. The tongues of a plurality of magnetic head suspensions formed on such a substrate therefore have warp.
In the process of bending the tongues, it is desired that the tongues of a plurality of magnetic head suspensions have a constant amount of warp so that the tongues of the magnetic head suspensions can be bent at a constant angle. Accordingly it is demanded that the variation in the warp is small among the individual regions on the long-sized substrate.
An object of the present invention is to provide a method for manufacturing magnetic head suspensions in which the variation in warp of the tongues of a plurality of magnetic head suspensions formed on a long-sized metal substrate can be reduced to increase the rate of acceptable pieces.
Another object of the present invention is to provide a method for inspecting metal substrates for magnetic head suspensions in which the variation in the warp of the tongues of a plurality of magnetic head suspensions formed on a long-sized metal substrate can be reduced to increase the rate of acceptable pieces.
The inventors of the present invention have carried out various experiments and considerations to find that there is a mutual relation between the variation in curvature of a long-sized metal substrate in its width direction and the variation in warp of the magnetic head supporting portions of a plurality of magnetic head suspensions formed on the metal substrate, and that using a long-sized metal substrate where the curvature variation in the width direction measured in its partial region is equal to or smaller than a given value reduces the variation among warps of the magnetic head supporting portions of a plurality of magnetic head suspensions formed on the metal substrate. The invention shown below has been made on the basis of the findings.
According to an aspect of the invention, a method for manufacturing magnetic head suspensions comprises the steps of: measuring a variation in curvature in a width direction of a long-sized metal substrate in its partial region; selecting a metal substrate where the variation in the curvature is not more than a given value; and forming a plurality of magnetic head suspensions by sequentially forming an insulating layer and a conductor layer on the selected metal substrate while conveying the metal substrate in its length direction.
When the variation in the curvature along the width direction of a long-sized metal substrate measured in its partial region is equal to or smaller than a given value, the variation in the warp is equal to or smaller than a certain value in areas along almost the whole length of the metal substrate. Accordingly the variation in the warp of the magnetic head supporting portions of a plurality of magnetic head suspensions can be small in almost the whole length of the metal substrate by selecting a metal substrate where the curvature variation along the width direction measured in its partial region is not more than a given value, and stacking an insulating layer and a conductor layer on the selected metal substrate to form a plurality of magnetic head suspensions. This increases the rate of acceptable pieces of the magnetic head suspensions and improves the precision in the process of bending the magnetic head supporting portions.
It is preferred that the given value is 2.0xc3x9710xe2x88x923 mmxe2x88x921 or less. In this case, the variation in the warp of the magnetic head supporting portions can be sufficiently reduced among the plurality of magnetic head suspensions formed on the long-sized metal substrate. Accordingly the rate of acceptable pieces of the magnetic head suspensions is further increased and the precision of the process of bending the magnetic head supporting portions is further enhanced.
It is preferred that the given value is 1.0xc3x9710xe2x88x923 mmxe2x88x921 or less. In this case, the variation in the warp of the magnetic head supporting portions can be sufficiently reduced among the plurality of magnetic head suspensions formed on the long-sized metal substrate. Accordingly the rate of acceptable pieces of the magnetic head suspensions is further increased and the precision of the process of bending the magnetic head supporting portions is further enhanced.
The step of forming the plurality of magnetic head suspensions may comprise a step of forming the plurality of magnetic head suspensions on the metal substrate in such a manner that the length direction of the plurality of magnetic head suspensions is parallel to the width direction of the metal substrate.
In this case, in the plurality of magnetic head suspensions formed on the metal substrate, the direction in which their magnetic head supporting portions are bent coincides with the direction of the warp of the metal substrate. Since the variation in the warp in the width direction is equal to or smaller than a certain value in almost the whole length of the metal substrate, the variation among the warps of the magnetic head supporting portions can be sufficiently reduced in the plurality of magnetic head suspensions formed on the metal substrate.
The metal substrate may be made of a stainless steel having a thickness of not less than 15 xcexcm nor more than 50 xcexcm. The metal substrate may be made of a stainless steel having a width of not less than 100 mm nor more than 500 mm. In these cases, by selecting a metal substrate where the curvature variation along the width direction measured in a partial region is not more than a given value, the variation in the warp of the magnetic head supporting portions of the plurality of magnetic head suspensions can be sufficiently reduced in almost the whole length of the metal substrate.
The step of measuring the variation in the curvature may comprise the steps of; extracting a plurality of stripe-like test pieces extended and arranged along the width direction of the partial region of the long-sized metal substrate, setting three or more measuring points on each of the extracted test pieces along their length direction, measuring heights of the three or more measuring points set on each test piece, obtaining a curvature of each test piece on the basis of the heights of the three or more measuring points measured for each test piece, and calculating the variation in the curvature from the curvatures of the plurality of test pieces.
The step of calculating the variation in the curvature may comprise a step of obtaining a difference between maximum and minimum values of the curvatures of the plurality of test pieces as the variation in the curvature.
The step of extracting the plurality of test pieces may comprise a step of etching the partial region of the long-sized metal substrate to remove the partial region except the plurality of test pieces.
The step of measuring the heights of the three or more measuring points may comprise a step of measuring the heights of the three or more measuring points set on each test piece by using a laser microscope.
According to another aspect of the present invention, a method for inspecting metal substrates for magnetic head suspensions comprises the steps of: measuring a variation in curvature in a width direction of a long-sized metal substrate in its partial region; and selecting a metal substrate where the variation in the curvature is not more than a given value as a metal substrate for the magnetic head suspensions.
When the variation in the curvature along the width direction of a long-sized metal substrate measured in its partial region is equal to or smaller than a given value, the variation in the warp is equal to or smaller than a certain value in areas along almost the whole length of the metal substrate. Accordingly the variation in the warp of the magnetic head supporting portions of a plurality of magnetic head suspensions formed on the metal substrate can be reduced by selecting a metal substrate where the curvature variation in the width direction measured in its partial region is not more than a given value as a metal substrate for the magnetic head suspensions. This increases the rate of acceptable pieces of the magnetic head suspensions and improves the precision in the process of bending the magnetic head supporting portions.
It is preferred that the given value is 2.0xc3x9710xe2x88x923 mmxe2x88x921 or less. In this case, the variation in the warp of the magnetic head supporting portions can be sufficiently reduced among the plurality of magnetic head suspensions formed on the long-sized metal substrate. Accordingly the rate of acceptable pieces of the magnetic head suspensions is further increased and the precision of the process of bending the magnetic head supporting portions is further enhanced.
It is preferred that the given value is 1.0xc3x9710xe2x88x923 mmxe2x88x921 or less. In this case, the variation in the warp of the magnetic head supporting portions can be sufficiently reduced among the plurality of magnetic head suspensions formed on the long-sized metal substrate. Accordingly the rate of acceptable pieces of the magnetic head suspensions is further increased and the precision of the process of bending the magnetic head supporting portions is further enhanced.
The metal substrate may be made of a stainless steel having a thickness of not less than 15 xcexcm nor more than 50 xcexcm. The metal substrate may be made of a stainless steel having a width of not less than 100 mm nor more than 500 mm. In these cases, by selecting a metal substrate where the curvature variation along the width direction measured in its partial region is not more than a given value, the variation in the warp of the magnetic head supporting portions of the plurality of magnetic head suspensions can be sufficiently reduced in almost the whole length of the metal substrate.
The step of measuring the variation in the curvature may comprise the steps of; extracting a plurality of stripe-like test pieces extended and arranged along the width direction of the partial region of the long-sized metal substrate, setting three or more measuring points on each of the extracted test pieces along their length direction, measuring heights of the three or more measuring points set on each test piece, obtaining a curvature of each test piece on the basis of the heights of the three or more measuring points measured for each test piece, and calculating the variation in the curvature from the curvatures of the plurality of test pieces.
The step of calculating the variation in the curvature may comprise a step of obtaining a difference between maximum and minimum values of the curvatures of the plurality of test pieces as the variation in the curvature.
The step of extracting the plurality of test pieces may comprise a step of etching the partial region of the long-sized metal substrate to remove the partial region except the plurality of test pieces.
The step of measuring the heights of the three or more measuring points may comprise a step of measuring the heights of the three or more measuring points set on each test piece by using a laser microscope.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.